Effects Of Hg,Zn,Cu And Ni Concentrations In Soil On The Concentrations Of Hg,Zn,Cu And Ni In Tobacco Roots And Leaves

A pot experiment was conducted to study effects of Hg,Zn,Cu and Ni concentrations and chemical forms in soil on Cd concentration in tobacco roots and leaves.The chemical forms of Hg,Zn,Cu and Ni in soil were extracted by Tessier sequential extraction.Zn,Cu and Ni concentrations in soil and tobacco were determined by inductively coupled plasma mass.Hg concentrations in soil and tobacco were determined by automatic dual channel atomic fluorescence photometer.The correlation between Hg,Zn,Cu and Ni concentrations of different chemical forms in soil and Cd concentrations in tobacco roots and leaves was analysed.The results will now be summarized as follows: 1.Effects of Hg concentrations in soil on Hg concentration in tobacco leaves and rootsWith the increasing concentrations of Hg applied to the soil,Hg concentrations of exchangeable,carbonate bound,Fe-Mn oxide bound,organic bound forms and residual state were significantly increased,and the Hg concentrations of exchangeable and carbonate bound form had significant positive correlation with the Hg concentrations of tobacco roots and leaves.Hg absorption coefficient of tobacco roots was low,and decreased with the increase of Hg concentration in soil;The transfer coefficient of Hg in tobacco were: lower leaves> middle leaves> upper leaves.Therefore,with the increasing concentration of Hg in soil,Hg concentrations in tobacco roots,lower leaves,upper middle leaves and leaves were significantly increased,and the order was: root> lower leaves> middle leaves > upper leaves.When the Hg concentration in soil was 1.098 mg·kg^-1,the Hg concentration of lower leaves（including Hg maximum）was 0.017 mg·kg^-1,this concentration was in the range of common Hg content in tobacco,so when the soil Hg concentration was less than 1.098 mg·kg^-1,the Hg content in tobacco leaves was in a safe range.2.Effects of Zn concentrations in soil on Zn concentration in tobacco leaves and roots With the increasing concentrations of Zn applied to the soil,Zn concentrations of five different chemical speciations were significantly increased,and the Zn concentrations of exchangeable and carbonate state had significant positive correlation with the Zn concentrations of tobacco roots and leaves.The absorption coefficient was increased with the increase of soil Zn concentration first,then decreased with the increase of Zn concentration;When the Zn concentration in soil was ≤100 mg·kg^-1,the transfer coefficient of Hg in tobacco were: upper leaves> middle leaves> lower leaves,and the order of corresponding Zn concentration in tobacco was: roots> upper leaves> middle leaves> lower leaves;When the Zn concentration in soil was ≥200 mg·kg^-1,the transfer coefficient of Hg in tobacco were: lower leaves> middle leaves> upper leaves,and the order of corresponding Zn concentration in tobacco was: roots> lower leaves> middle leaves> upper leaves;so when the soil Zn concentration was less than 154.3 mg·kg^-1,upper leaves,middle leaves and lower leaves in the average concentration of Zn < 23.53mg·kg^-1,this Zn concentration might be in the safe range in tobacco leaves.3.Effects of Cu concentrations in soil on Cu concentration in tobacco leaves and rootsWith the increasing concentrations of Cu applied to the soil,Cu concentrations of exchangeable,carbonate bound,Fe-Mn oxide bound,organic bound and residual state were significantly increased,and the Cu concentrations of exchangeable and carbonate state had significant positive correlation with the Cu concentrations of tobacco roots and leaves.The absorption coefficient was increased with the increase of soil Cu concentration first,then decreased with the increase of Cu concentration;The transfer coefficient of Cu in tobacco are: upper leaves> middle leaves> lower leaves.Therefore,with the increasing concentration of Cu in soil,Cu concentrations of tobacco roots,lower leaves,upper middle leaves and leaves were significantly increased,and the order is: root> lower leaves> middle leaves > upper leaves.When the Cu concentration in soil was ≤ 72.63 mg·kg^-1,upper leaves,middle leaves and lower leaves in the average concentration of Cu≤9.49 mg·kg^-1,this Cu concentration in tobacco leaves might be in the safe range.4.Effects of Ni concentrations in soil on Ni concentration in tobacco leaves and rootsWith the increasing concentrations of Ni applied to the soil,Ni concentrations of five different chemical speciations were significantly increased,and the Ni concentrations of exchangeable and carbonate state had significant positive correlation with the Ni concentrations of tobacco roots and leaves.The absorption coefficient was increased with the increase of soil Ni concentration first,then decreased with the increase of Ni concentration;The transfer coefficient of Ni in tobacco are: lower leaves> middle leaves> upper leaves.Therefore,with the increasing concentration of Ni in soil,Ni concentrations of tobacco roots,lower leaves,upper middle leaves and leaves were significantly increased,and the order is: root> lower leaves> middle leaves > upper leaves.When the Ni concentration in soil was below 122.3 mg·kg^-1,upper leaves,middle leaves and lower leaves in the average concentration of Ni< 3.43 mg·kg^-1,he Ni content in tobacco leaves might be safe.